1. Field of the Invention
The present invention relates to a device for clamping an edge of a plate for a printing machine, more specifically, a device for inserting and fixing the edge of the plate between a base and an opening and closing part.
2. Description of the Prior Art
[The first prior art]
FIG. 15A, FIG. 15B FIG. 15C and FIG. 15D show a device for clamping an edge of a plate for a printing machine (hereinafter referred to as the first prior art device) which have been conventionally used. A leading edge side lower plate 72, a leading edge side upper plate 73, a tail edge side lower plate 74 and a tail edge side upper plate 75 are provided in a groove 71 formed on a plate cylinder 70. The leading edge side upper plate 73 can be opened and closed to the leading edge side lower plate 72, and the tail edge side upper plate 75 can also be opened and closed to the tail edge side lower plate 74. Also, both the tail edge side lower plate 74 and the tail edge side upper plate 75 can be rotated in directions of an arrow 90 and an arrow 91 as one united body by centering around a central point 75J.
A pressure roller 76 is provided adjacent to the plate cylinder 70. The pressure roller 76 can also be rotated in both directions of the arrow 90 and the arrow 91 by centering around a central point 76J. A bent strip 77 provided adjacent to the pressure roller 76 can be moved together with the pressure roller 76.
In case of disposing the plate 50 on a cylinder surface 70G of the plate cylinder 70, a leading edge side part 50a of the plate 50 is inserted between the leading edge side lower plate 72 and the leading edge side upper plate 73 (FIG. 15A). Then, the leading edge side upper plate 73 is closed to the leading edge side lower plate 72, so that the leading edge side part 50a of the plate 50 is clamped and fixed therebetween. Upon fixing the leading edge side part 50a, the pressure roller 76 is rotated in the direction of the arrow 91 by centering around a central point 76J. The plate cylinder 70 is rotated in the direction of the arrow 90 under that condition.
The plate 50 is disposed on the cylinder surface 70G of the plate cylinder 70 by rotating the plate cylinder 70 in the direction of the arrow 90. As shown in FIG. 15B, the plate 50 is pressed onto the cylinder surface 70G when the plate 50 is disposed on the cylinder surface 70G of the plate cylinder 70.
As a result of rotating the plate cylinder 70, a tail edge side part 50b of the plate 50 is positioned adjacent to the tail edge side lower plate 74 and the tail edge side upper plate 75 as shown in FIG. 15C. Rotation of the plate cylinder 70 is suspended at that position, and the bent strip 77 is moved in the direction of the arrow 91 from the condition. Movement of the bent strip 77 is controlled by actuation of a cylinder (not shown) connected to the bent strip 77.
The tail edge side part 50b of the plate 50 is pushed in the direction of the arrow 91 with the nose of the bent strip 77. As a result, the tail edge side part 50b of the plate 50 is directed to a space 78 formed between the tail edge side lower plate 74 and the tail edge side upper plate 75 as shown in FIG. 15D.
Both the tail edge side lower plate 74 and the tail edge side upper plate 75 are rotated in the direction of the arrow 90 by centering around the central point 75J. The tail edge side part 50b of the plate 50 is inserted between the space 78 by the rotation. Then, the tail edge side upper plate 75 is closed to the tail edge side lower plate 74, so that tail edge side part 50b of the plate 50 is clamped and fixed therebetween.
Upon disposing the plate 50 on the plate cylinder 70 as described above, both the tail edge side lower plate 74 and the tail edge side upper plate 75 are automatically returned to their original positions by rotating around the central point 75J. As a result, the tail edge side part 50b of the plate 50 is pulled in the direction of the arrow 91. Thus, the plate 50 is fitted tightly on the cylinder surface 70G of the plate cylinder 70 as a result of applying tension.
[The second prior art]
Another device for clamping an edge of a plate for a printing machine (hereinafter referred to as the second prior art device) which have been conventionally used will be described herein with reference to FIG. 16. FIG. 16 is a sectional side elevation which shows the periphery of a tail edge side lower plate 84 and a tail edge side upper plate 85. Both the tail edge side lower plate 84 and the tail edge side upper plate 85 are mounted in a groove 81 formed on a plate cylinder 80.
A rack gear 83 is fixed to the tail edge side lower plate 84 as one united body. All the rack gear 83, tail edge side lower plate 84 and the tail edge side upper plate 85 are movable in directions of an arrow 92 and an arrow 93. Further, a plurality of coil springs 79 are provided into the tail edge side lower plate 84, so that the tail edge side lower plate 84 is pushed in the direction of the arrow 92 with the coil springs 79.
On the other hand, a driving shaft 82 is connected rotatably to the plate cylinder 80. A pinion gear 82G is fixed to the driving shaft 82. The pinion gear 82G is engaged with the rack gear 83. In other words, both the tail edge side lower plate 84 and the tail edge side upper plate 85 are moved in the directions of the arrow 92 and the arrow 93 through both the pinion gear 82G and the rack gear 83 in accordance with the rotation of the driving shaft 82.
Both the tail edge side lower plate 84 and the tail edge side upper plate 85 are in a retracted position in the direction of the arrow 92 when a tail edge side part 50b of the plate 50 thus disposed on the cylinder surface of the plate cylinder 80 is positioned adjacent to the tail edge side lower plate 84 and the tail edge side upper plate 85.
Further, a blade 87 is provided adjacent to the plate cylinder 80. The tail edge side part 50b of the plate 50 is pushed into the groove 81 by the movement of the blade 87 in a direction of an arrow 94. Both the tail edge side lower plate 84 and the tail edge side upper plate 85 are moved toward in the direction of the arrow 93 by the rotation of the driving shaft 82 from the condition.
Thus, the tail edge side part 50b of the plate 50 is inserted into the space formed between the tail edge side lower plate 84 and the tail edge side upper plate 85 by the movement of the plates. FIG. 16 is a view illustrating insertion of the tail edge side part 50b into the space.
Then, the tail edge side upper plate 85 is closed to the tail edge side lower plate 84, so that the tail edge side part 50b of the plate 50 is clamped and fixed therebetween. Upon fixing the tail edge side part 50b, both the tail edge side lower plate 84 and the tail edge side upper plate 85 are moved in the direction of the arrow 92 with clamping the tail edge side part 50b therebetween. Thus, the plate 50 is fitted tightly on the cylinder surface of the plate cylinder 80 as a result of applying tension.
However, the devices of the first prior art device and the second prior art device described above have following problems to be resolved. In the device of the first prior art shown in FIG. 15, the device need to carry out following steps in order to clamp and fix the tail edge side part 50b. One of the steps is to insert the tail edge side part 50b between the space 78 formed between the tail edge side lower plate 74 and the tail edge side upper plate 75 by rotating both the plates in the direction of the arrow 90. Another step is to clamp and fix the tail edge side part 50b between the plates by closing the tail edge side upper plate 75 to the tail edge side lower plate 74 after the insertion.
As described above, these two steps need to be carried out separately. Therefore, it takes much time to complete these steps. Further, in order to carry out the steps described above, much complicated mechanisms and control are required to the device of the first prior art device.
Still further, stopping accuracy of the rotation of the plate cylinder 70 and positioning accuracy of the tail edge side part 50b guided with pressure of the bent strip 77 are required in order to insert the tail edge side part 50b between the space 78 having relatively narrower width. The tail edge side part 50b can not be inserted between the space 78 even when both the tail edge side lower plate 74 and the tail edge side upper plate 75 are rotated in a direction of the arrow 94 in case of carrying out inaccurate positioning of the tail edge side part 50b and/or insufficient stopping accuracy of the rotation of the plate cylinder 70.
Therefore, the plate cylinder 70 can not be rotated in a high speed for maintaining stopping accuracy of the plate cylinder 70. As a result, work efficiency of the printing work is decreased. Further, there is a higher probability that the tail edge side part 50b is not inserted reliably between the space 78 when the tail edge side part 50b of the plate 50 is curved outwardly or inwardly.
Also, the second prior art device shown in FIG. 16 have similar problems to that of the first prior art device described above. The tail edge side part 50b is inserted into the space formed between the tail edge side lower plate 84 and the tail edge side upper plate 85 by moving both the plates 84 and 85 in the direction of the arrow 93 after pushing the tail edge side part 50b with the blade 87 in the direction of the arrow 94. Then, the tail edge side part 50b must be fixed by closing the tail edge side upper plate 85 to the tail edge side lower plate 84.
In order to fix the tail edge side part 50b, the device need to carry out the following steps. One of the steps is to move both the tail edge side lower plate 84 and the tail edge side upper plate 85 in a direction of the arrow 93. Another step is to close the tail edge side upper plate 85 to the tail edge side lower plate 84. It take much time to complete these steps, and much complicated mechanisms and control are required to the device of the second prior art. Further, there is a higher probability that the tail edge side part 50b is not inserted reliably between the space even when both the tail edge side lower plate 84 and the tail edge side upper plate 85 are moved in a direction of the arrow 93 in case of occurring outward/inward curvature of the tail edge side part 50b.